Polybenzimidazole (PBI) constitutes a well-known class of heterocyclic polymers and is described, merely by way of example and not limitation, in U.S. Pat. No. 4,898,917 issued to Sansone. One PBI known as poly-2,2′(m-phenylene)-5,5′-bibenzimidazole has been used, as well as other PBI compounds, to form ionically conductive materials, fire resistant materials, and various types of separatory media, such as membranes and ultrafilters. Poly-2,2′(m-phenylene)-5,5′-bibenzimidazole is resistant to strong acids, bases, and high temperatures up to 500° C., but exhibits very poor solubility in common organic solvents. It is soluble under harsh conditions in highly polar, aprotic organic solvents, such as dimethyl sulfoxide (DMSO), N,N-dimethylacetamide (DMAc), N,N-dimethylformamide (DMF), and N-methylpyrrolidinone (NMP), which exhibit high boiling points and low vapor pressures. Accordingly, such solvents are not preferred for polymer processing.
As such, it would be advantageous to modify a PBI, such as poly-2,2′(m-phenylene)-5,5′-bibenzimidazole, to exhibit better solubility in common organic solvents more preferable for polymer processing. Also, an appropriate method for modifying PBI would be advantageous.